The present invention relates to a vaccine and methods for the treatment of Motor Neurone Diseases (MND), particularly amyotrophic lateral sclerosis (ALS).
Motor Neurone Disease (MND) is the name given to a group of related diseases affecting the motor neurones in the brain (upper motor neurons) and spinal cord (lower motor neurons). Motor neurones (or motor neurons) are the nerve cells along which the brain sends instructions, in the form of electrical impulses, to the muscles. Degeneration of the motor neurones leads to weakness and wasting of muscles. This generally occurs in arms or legs initially, some groups of muscles being affected more than others.
There are several classifications of MND. In most cases of MD, degeneration of both the upper and lower motor neurones occurs. This condition is called Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig's disease, and is characterized by muscle weakness, stiffness and fasciculations (muscle twitching). There are also less common forms in which a more selective degeneration of either the upper motor neurones (such as Primary Lateral Sclerosis, PLS) or lower motor neurones (such as Progressive Muscular Atrophy, PMA) is observed. Progressive Bulbar Palsy (PBP or Bulbar Onset) is a version of ALS that starts with difficulties in swallowing, chewing and speaking and affects approximately 25% of ALS patients.
There is considerable overlap between these forms of MND. People with PMA in time develop upper motor neurone involvement and in both PMA and ALS some people may eventually experience speech and swallowing difficulties in varying degrees (bulbar onset ALS or PMA).
ALS, is a chronic, progressive neurodegenerative disease characterized by gradual degeneration of the nerve cells in the central nervous system (CNS) that control voluntary muscle movement. The progressive loss of motor neurons leads to gradual skeletal muscle atrophy and to inevitable death, usually within 2-3 to ten years of the disease onset. Muscular weakness and atrophy and signs of anterior horn cell dysfunction are initially noted most often in the hands and less often in the feet. The site of onset is random, and progression is asymmetric. In the U.S.A. alone, 30,000 people currently have ALS and about 8,000 new cases are diagnosed each year.
ALS occurs in sporadic (SALS) and familial (FALS) forms (Mulder et al., 1986; Munsat, 1989). The primary risk factors are mostly unknown, yet 5 to 10% of all ALS patients are familial (FALS). About 20% of all familial forms were found to have mutations in the gene encoding Cu/Zn superoxide dismutase type 1 on chromosome 21 (Rosen et al., 1993; Brown, 1995). SOD is an enzyme that catalyzes the conversion of superoxide anions to hydrogen peroxide, and thus SOD can protect cells against the deleterious effects of these toxic radicals. It appears that the toxicity of different SOD mutants is not due to decreased free-radical scavenging activity since no correlation was found between enzymatic activity, polypeptide half-life and resistance to proteolysis with age of onset or rapidity of human disease progression (for review, see Julien, 2001). Transgenic mice expressing various SOD1 mutants developed motor neuron disease and thus constitute an accepted animal model for testing ALS and other motor neurone therapies.
Recently, a new ALS gene has been identified by two independent groups of scientists (Hadano et al., 2001; Yang et al., 2001). This new gene, called ALS2, is located on chromosome 2 and encodes for a protein named alsin. The new ALS2 gene is mutated in both people with juvenile amyotrophic lateral sclerosis (JALS), also known as ALS2, and people with juvenile primary lateral sclerosis (JPLS). Mutations in different regions of the chromosome are associated with different motor neuron diseases. Specifically, a mutation in one region is found in people with ALS, while mutations in two other regions are found in people with JPLS. In the future, transgenic mice carrying these mutations will certainly constitute a further model for testing ALS therapies.
Numerous studies over the last decade have been devoted to understanding the etiology, prognosis and progression of the disease. No consensus has been reached, except for admitting that it is a multi-factorial disease in terms of circumstances leading to its progression, while the etiology remains unclear.
It is evident today that many of the factors which contribute to the progression of ALS are found in many other chronic and acute neurodegenerative disorders. These factors include oxidative stress, excitotoxicity, deprivation of trophic support, and ionic imbalance. Over the years attempts have been made to halt the progression of ALS, as in other chronic and acute neurodegenerative disorders, by blocking different mediators of cytotoxicity. Most of these clinical trials have had negative results (Turner et al., 2001).
Oxidative stress is characterized by accumulation of free radicals that can lead to motor neuron death. Free radicals damage components of the cells' membranes, proteins or genetic material by “oxidizing” them. These free radicals may be generated when the enzyme SOD malfunctions, either because of genetic mutation as occurs in some familial ALS patients or because of the chemical environment of the nerve cells, or they may be generated as a result of glutamate excitotoxicity, or for some other reason. Many ALS patients take Coenzyme Z Q10 and Vitamin E in all effort to neutralize free radicals.
Glutamate is one of the most common mediators of toxicity in acute and chronic degenerative disorders (Pitt et al., 2000) like status epilepticus, cerebral ischemia, traumatic brain injury, ALS, Huntington's chorea, lathyrisms and Alzheimer's disease. Glutamate is a primary excitatory neurotransmitter in the human CNS. L-glutamate is present at a majority of synapses and is capable of displaying dual activity: it plays a pivotal role in normal functioning as an essential neurotransmitter, but becomes toxic when its physiological levels are exceeded.
For spinal motor neurons, rapid glutamate removal following synaptic activity is accomplished by the glutamate transporter EAAT2 present in astrocytes. Decrease in EAAT2 activity and protein level was found in brain tissue of ALS patients (Rothstein et al., 1992), This could lead to increased extracellular concentration of glutamate and death of motor neurons. Clinically, the beneficial effect of Riluzole, a glutamate release inhibitor, on the course of the disorder in both humans and transgenic mice, led to the approved drug treatment of ALS. However, in neutralizing the toxic effect it is likely to interfere with the physiological functioning of glutamate as a ubiquitous CNS neurotransmitter.
The role of immune factors, cellular and molecular, in ALS has been debated over the years. It has been argued, as in many other neurodegenerative diseases, that inflammation is associated with the disease propagation, and the usage of immunosuppressive drugs in ALS has been suggested. Also, in many ALS patients, a correlation was observed with the presence of anti-ganglioside antibodies, which led some researchers to suggest that ALS is an autoimmune disease. However, no conclusive evidence has been provided to support this hypothesis.
In the laboratory of the present inventors, it has been recently observed that under neurodegenerative conditions caused by mechanical (axotomy) or biochemical (glutamate, oxidative stress) insults, the immune system plays a critical role. Thus, it has been found that activated T cells that recognize an antigen of the nervous system (NS) promote nerve regeneration or confer neuroprotection. Reference is made to PCT Publication No. WO 99/60021, the entire contents of which is hereby incorporated herein by reference. More specifically, T cells reactive to MBP were shown to be neuroprotective in rat models of partially crushed optic nerve (Moalem et al, 1999) and of spinal cord injury (Hauben et al, 2000). Until recently, it had been thought that the immune system excluded immune cells from participating in nervous system repair. It was quite surprising to discover that NS-specific activated T cells could be used to promote nerve regeneration or to protect nervous system tissue from secondary degeneration which may follow damage caused by injury or disease of the CNS or peripheral nervous system (PNS).
It was further observed by the present inventors that stressful conditions in the CNS harness the adaptive immune response to cope with the stress and that this response is genetically controlled. Thus, the survival rate of retinal ganglion cells in adult mice or rats after crush injury of the optic nerve or intravitreal injection of a toxic dosage of glutamate was shown to be up to two-fold higher in strains that are resistant to CNS autoimmune diseases than in susceptible strains. The difference was found to be attributable to a beneficial autoimmune T cell response that was spontaneously evoked after CNS insult in the resistant but not in susceptible strains. Thus, the survival rate of neurons as a result of such an insult is higher when T cell response directed against self is evoked, provided that it is well-regulated. In other words, it was demonstrated that a protective autoimmune response is evoked to oppose the stressful conditions so as to protect the animal from the insult consequences. It was further observed that in animals with an impaired ability to regulate such a response, or in animals devoid of mature T cells (as a result of having undergone thymectomy at birth), the ability to cope with the stressful conditions is reduced. Consequently, the survival rate of neurons following CNS insult in these animals is significantly lower than in animals endowed with an effective mechanism for mounting protective autoimmune T cell-mediated response (Kipnis et al., 2001).
It was then further found by the present inventors that vaccination with non-pathogenic synthetic copolymers that resemble self-proteins such as Copolymer 1 (Cop 1 or Glatiramer), a random copolymer composed of the four amino acids: tyrosine-glutamate-alanine-lysine (hereinafter “Cop 1”), and poly-Glu, Tyr (hereinafter “PolyYE”), and by T cells activated thereby, after traumatic CNS insult can be used to boost the protective autoimmunity and thereby to reduce further injury-induced damage, and can further protect CNS cells from glutamate toxicity. Reference is made to our previous U.S. patent application Ser. Nos. 09/756,301 and 09/765,644, both dated 22 Jan. 2001, herein incorporated by reference in their entirety as if fully disclosed herein, corresponding to WO 01/93893, which disclose that Cop 1, Cop 1-related peptides and polypeptides and T cells activated therewith protect CNS cells from glutamate toxicity (U.S. Ser. No. 09/756,301) and prevent or inhibit neuronal degeneration or promote nerve regeneration in the CNS or PNS (U.S. Ser. No. 09/765,644). Reference is further made to our previous U.S. patent application Ser. No. 09/893,344 dated 28 Jun. 2001, herein incorporated by reference in its entirety as if fully disclosed herein, which discloses that the copolymer poly-Glu50Tyr50, formerly called polyGT and also designated PolyYE, and T cells activated therewith, protect CNS cells from glutamate toxicity and also prevent or inhibit neuronal degeneration or promote nerve regenetion in the CNS or PNS. Specifically, it was shown in said applications that in optic nerve fibers, the number of surviving retinal ganglion cells was significantly higher in the Cop 1-immunized or poly-Glu, Tyr-immunized mice than in the mice injected with PBS.
The sole drug approved and currently available for treatment of ALS is Riluzole (2-amino-6-(trifluoromethoxy)benzothiazole), a putative blocker of glutamate release, which appears to have some spasm-reducing effects in this condition, possibly through inhibition of glutamatergic transmission in the CNS. It is administered orally in the form of tablets. Riluzole does not cure the disease or improve symptoms. It exerts a modest to significant effect in ALS patients by elongating their life span for about 3 months, but does not improve muscular strength or neurologic function.
It would be highly desirable to provide further medicaments for the treatment of motor neuron diseases, including ALS.
Citation or identification of any reference in this section or any other part of this application shall not be construed as an admission that such reference is available as prior art to the invention.